This invention relates to an armature for an electric rotary machine and a method of manufacturing such an armature, and particularly to an armature having half-closed slots adapted to effectively prevent the winding from being displaced.
Armatures having half-closed slots for preventing the winding from being displaced when used in an electric rotary machine are disclosed, for example, in U.S. Pat. No. 3,586,893 and Japanese Patent Laid-open No. 52-9805, wherein such slots are formed by pressing or bending the projections preliminarily formed near the openings of said slots.
However, the prior art involves drawbacks, as follows.
When the projection is bent into the slot, the tip of the projection may damage the insulator coating on the winding placed in the slot, thereby causing dielectric breakdown. Especially in case of a projection provided at its side with a slit, it has less mechanical strength and may be broken during a high speed operation. If the half-closed slot is to be formed by pressing a semi-circular projection, it is necessary to apply larger bending force by using a larger machine, or its circumferential area may become rough and adversely affect the uniformity of magnetic reluctance of the armature.